The League has seemed to move through a set cycle, reboot or not, since the late 1970's: a line-up fronted by one or more of the 'Big Three' (Superman, Wonder Woman, and Batman) makes the book popular; some or all of them leave; the book becomes less popular as lesser-known heroes take over; the book gets cancelled and then relaunched with one or more of the Big Three; and so on, and so forth.
Johns and Lee certainly make this an event book again, as the League forms for the first time to combat a massive alien invasion. Along with the usual suspects (Superman, Batman, Wonder Woman, Aquaman, Flash, and Green Lantern) and without original founding member Martian Manhunter, the league's seventh founding member turns out to be Cyborg in this iteration.
Historically, Cyborg did appear on the 1980's version of Super Friends, and he is a founding member of the League on Smallville. And he's African-American, which make the League look a little less white.
A lot of things blow up. Much Marvel-style bickering and posturing occurs among the superheroes before they figure out how to work together. Humanity, afraid of these relatively new super-heroes, comes to embrace them after they see them battling aliens in defence of humanity.
Lee's often hilariously fussy costume redesigns are distracting and often far goofier than previous iterations. His Darkseid is especially ugly, fussy, and over-complicated. Not much of interest happens here, but it happens loudly and repeatedly for emphasis. Lightly recommended.